Place the sugar and mint leaves in a food processor and process until mint has been finely minced. Remove any tough parts that have not been processed.
Add the cubed watermelon, lime juice and pinch of salt.
Puree until smooth (total amount of liquid is about 4 cups, as per markings on food processor).
Pour watermelon puree mixture in a shallow stainless steel pan and place in freezer.
Stir to break up the ice every 60 minutes or so (with a fork) for 3-4 hours. The consistency should be granular but still slushy.
At this point, cover and allow to freeze undisturbed for at least 2 hours.
When ready to serve, grate the top (with a fork) and place in serving dish.
Decorate with mint leaves and lime wedge (if desired).
Feel free to adjust the amount of sugar that you add according to personal preference.Please keep in mind that the nutritional information provided below is just a rough estimate and variations can occur depending on the specific ingredients used.